The present invention generally relates to apparatus and methods for hydraulic automatic control valves and more particularly, to apparatus and methods for such valves with spring-less diaphragms.
Automatic hydraulic control valves pose several design challenges. First, they require position indicators for displaying the valve opening rate, i.e. how high above the seat the hydraulic control valve is. These position indicators are typically comprised of a stem that sticks up and reflects the vertical position of the diaphragm. These indicators are vulnerable to being struck on the side and bent by elements such as control tubing associated with the valve. These indicators are also prone to leakage because they are hard to seal since they bob up and down from a wet area inside the valve to a dry area outside the valve, where the indicator is subject to being covered with dirt which wears out the seal.
Second, there is a general problem of how to put a valve seat comprised of a stainless steel ring into the internal coated surface of the valve without penetrating the coating, which causes rust damage.
A third problem is that above the cover of the valve is a significant amount of control equipment associated with the valve, such as solenoids, pressure pilots and control tubing that has to be connected to the cover of the valve. In order to inspect the diaphragm inside the valve, the valve cover must be removed and this requires dismounting the significant amount equipment each time the inspection is performed. In addition, installation of the valve covers may be further complicated by the need to position the control mouth within the control chamber at its highest point for air removal.
A further design issue with hydraulic control valves having single chamber actuators is designing a spring that triggers the valve closing on minimal differential pressure across the valve. A still further design issue is how to design drainage of the upstream and downstream portions of the valve in a convenient manner for a variety of systems the location of whose drain piping or other components may not be known in advance. Finally, the number of parts should be minimized for and for performance reasons and for cost reasons, since each part has to be designed, manufactured, tested, inspected, etc.
There is an ongoing need for improved design of hydraulic control valves and position indicators for such valves.